Apparatus for precision grinding



p 23, 1952 c. T. RHODES 2,611,221

APPARATUS FOR PRECISION GRINDING Filed March 9, 1951 A fl-rpoe/n/b'm/ J CLEMENT I RHODES :15 Z 5 5 MM 2% Patented Sept. 23, 2952 UNITED STATES V O F 7 FOR PRECISIQNDING Y Clement- Tipton Rhodes; Ascot, England s puesam Mei-en 9, unseen No. 2 14,713 --In- Great Britain April 12, 1959 .14 claims (01. 51+I0'3) f1 This invention relates: to apparatus" for pre-' cision grinding and more; particularly. for the precision grinding of. parts which. are required engine fuel injection pumps or atomisers andof so-called grinding laps fon-t'ruing the seats of such valves; v

The well known dieseiengine iuelainjection pumps and atomisersznow" in widespread use include. needle: valves the seats of which. are required tube of a slightly' difiei'ent angle- (say, half a degree) from that of the. needle. For example, it is common practice in; atomiser needle valves to-make the angle: of the needle 60 and the angle of the seat 59 thesdifierenoe of- V being adopted :to ensure the: necessary narrow ring-likecontact. Because of this difference-of angle slight as'itis, it is not possible to grind theneedle directlyiin to the seat as-is done, for. example withinternal combustion engine poppet valves. Theusual practice therefore is to grind the'seats by meansvof a grinding lap of the correctseat angle. Owing to the highdegree of accuracy required and'in particular owing to the high; degree of concentricity required between the" tapered end of; such a lap and the body or shank thereof; the" grinding ofsuch-laps-presents a quite-serious problem" and has hitherto had to be done by more-or less expensive and complex grinding-machinery; A similarly difllcult problem" arises inconnection' with the grinding of the needles themselves. Indeed,shither-to, when. a; needle or lap has{ been required to "be ground it has had to be done attthez factory making the pump or atomiser' in question; the precisionrequired being beyond the capabilities of "mostordinaryworkshops especially in "remote" or -countrydistricts; This is a serious practical defect since, of course. theseneedles and valve" seats'a're. subjected" to considerable" wear." andliavef to be? regroun'd and true'd fairlyfrequeritliz. The re'sent invention seeks to provide improved? apparatus for grinding which. shall enable-I devices .such as the I laps and' needles abovementionedl-tohe easily and accurately ground.

The present invention isprimarily intended for use in conjunction with amachine -as: de-

scribed -in- U. I S};- application Serial No. 211 247 to enable such a machine to beqsetwup accurately to grind a needle or lap'toa-predetermined angle. The said 'co-pending- 1 application describes a machine for the precision grinding of an article required to have-a circular sectioned part accurately ground in accurate-concentricitywith another circular sectioned part, said machine comprising a grinding 'wheel-,-. a block having a hardened recess-"preferably a v recessadapte'd Y to receive the former part with the latter in contact with the grinding? wheeland: a friction wheel'arranged' to press said latter part in saidv recess and simultaneously-to rotate it in the recess by friction drive transmitted thereto.

According to this inventionthe recessed block in a machine as above set forth'iscarried in an angularly adjustable member which is associated-with an index and-scale; saidscale-andindex being relatively adjustable with respect to one: another and" there is provided for setting up the machine with: the block in a desired angular relationship with the axis =ofthegrinding. wheel asector or triangularly shaped: gauge (hereinafter termed taper-gauge ofpredetermined apeangle one edge of which is arranged: to lie in the recess in theblook or'alternatively against the work when in the block and another edge of which lies;: when the carrier v member is correctly. angularly. adjusted tothe sector gauge. The index and scale maythenbe adjusted to read thati'angle, the adjustment fixed and the index and scale used to ad.- just to any angle-within the range of reading.

The expression sector shaped :or triangular 1y shaped? as appliedto the taper gauge is em-- ployed in-a wide sense and isr noti intended: to.

limit the invention. to taper: gauges which are of sector or triangle shape int-he-strict: geometri calsense. Anyigauge of generally fiatroriapproximately fiatzform witli -two main straight edge: lengths at a: predetermined apex angle to one another 11$ 1 seo'tor' -i .shapedl or itriang ular ly'" shaped gauge within the meaning of this specification even though, for example, the said edge lengths do not meet at a point.

The invention accordingly provides a taper gauge having two edges which are inclined to one another at the angle desired in the taper. One of these edges may be splayed so that in section it provides a V which is more or less a mirror image of the V in the work block so that in use this v may be positioned to lie against the shank of a needle or lap to be ground and which is placed in the work block. Alternatively the said edge may be made of part cylindrical section corresponding to the section of the shank of a needle or lap to be ground so that the arcuate edge of the gauge can be placed, instead of the work, in the V of the block.

The invention is illustrated in the accompanying drawings in which Figure 1 is a perspective view, Figure 2 is a grinding lap, Figure 3 shows another form of template, and Figure 4 is an elevation of the whole machine.

Referring to the drawings the machine therein shown is generally in accordance with the showing in my co-pending application Serial No. 211,247 and comprises a motor 1 driving an emery or other grinding wheel 2, a work holder 3 carrying a block 4 having a hardened V recess 5 in which the shank of the work to be ground may be placed, and a swivel work head adapted to carry and to drive a shaft I21 upon which is a rubber or similar disc or wheel I20 which is adapted to press the shank of the work into the block and simultaneously rotate said work, the whole arrangement being such that the part of the work to be ground is held against the grinding wheel and rotated during the grinding by friction drive transmitted to the shank. The swivel work head shaft and rubber wheel are driven from the motor I in a manner which need not be described here, being fully described in my co-pending application referred to. A typical example of work to be ground is shown in Figure 2 which illustrates a grinding lap having ashank l and aconcentric tapered end II which must be accurately ground. The work holder is angularly adjustable about a vertical axis as set forth below so that the angle at which the work is presented to the grinding wheel may be adjusted as desired. The adjustment can be locked in any convenient way, e. g. by a clamp, by operating a locking handle.

In applying the present invention to a precision grinder as above described the work holder is angularly adjustable about the vertical pivot'axis l2 and is provided with a radial arm [4 the other end of which has an index mark reading against 'a scale- IS. The position of rotation of the arm M is determined by an abutment micrometer screw I 1 on which is a micrometer head l8 which can be adjustably rotated with respect to the screw and locked in any-position by a lock nut [9. The head I8 carries a scale 20 reading against a mark 2 I. For example the-main scale [6 may be marked in degrees and the scale 20 in minutes, one revolution of the head (when locked to the screw l7) giving the appropriate alteration of the position of the arm. A second abutment screw 22 enables the arm to be pressed up against the screw [1 after adjustment thereof. The main scale is adjustable in position over a small angle, being held by screws 23 which pass through slotted holes in the scale member. There is also provided for use in setting up the machine a taper gauge in'the form of a. generally 4 flat metal plate; one edge may be splayed out into a V as shown at 24 in Figure 3 so that it will rest against the shank of a lap or needle in the V of the block or may be cylindrically formed as shown at 25 in Figure 1 so that it can rest directly in the V in place of a lap or needle.

The taper gauge used in any particular case is chosen to have an included angle between the two angularly related straight edges which is exactly a predetermined known angle. In use a socalled micrometer gauge clock 26 is mounted temporarily on a member 21 temporarily attached to the spindle of the grinding wheel and the taper gauge is placed with the splayed V edge or the cylindrical edge on the shank of the work in the V of the block or in the V of the block (as the case may be). The work holder is then angularly adjusted until the plain edge of the taper gauge is parallel to the axis of the grinding wheel. This may be tested for by adjusting the micrometer gauge clock until its feeler point is in contact with the plain edge of the taper gauge and then moving the work head in a direction parallel to the grinding wheel axis by the. normally. provided longitudinal traversing mechanism operated by the normally provided handle (not shown) which moves the work head along the bed of the grinding machine. When the work holder is correctly adjusted to its proper position the plain edge of the taper gauge will slide along the feeler point and the reading at the gauge clock will remain constant during this sliding action. When this has been done the angular setting will correspond to the apex angle of the taper gauge and the main scale I6 and micrometer head [8 may. then be adjusted until the scales l6 and 20 jointly read this angle correctly. They may then be locked and the machine is set up ready for use and can be adjusted. by means of the scales to grind any angle within the scale range.

The invention provides two most important practical advantages. The first is that it enables the grinding machine to be correctly set up either against the workwhen actually in position or against the work block. The second advantage is that the operator can readily test for faults such, for example, as grinding wheel bearing faults in the machine itself.

In practice the invention greatly facilitates accurate grinding and enables what would otherwise be the difficult and lengthy operation of setting up the grindingmachine to grind a taper oi predetermined angle to be performed quickly and with comparative easeby comparatively unskilled and semi-skilled labour.

l. Amachine for the precision grinding of an article required-to have a circular sectioned part accurately ground in concentricity with another circular sectioned part comprising a grinding wheel, a recessed block having a hardened recess adapted to accommodate the second mentioned part with the first mentioned part in contact with said grinding wheel, an angularly adjustable member carrying said block and adjustable about an axis perpendicular to the axis of the grinding wheel, said member having a radial arm, a friction engagement wheel for engaging said second mentioned part and holding it in the recess, means for rotating said friction wheel to rotate said second mentioned part in said recess, means for locking said member in any position of adjustment, scale and-co-operating index means one of which moves with said member and indicates the movement thereof against the other. and means for adjusting and fixing in any position of adjustment the position of one of said means to adjust the scale reading for any given position of adjustment of said member, said scale and co-operating index means including an index on said arm and reading against an angularly adjustable but otherwise fixed scale, a micrometer screw, said arm abutting against the end of said micrometer screw, a drum head carried by said screw provided with a fine reading scale reading against a second index, said head being rotatably adjustable on said screw and provided with means for locking the same to the screw in any position of relative adjustment.

2. A machine, as claimed in claim 1 wherein the end of the arm abuts against the end of the micrometer screw and is positioned between said end of said micrometer screw and the end of a second screw.

3. A machine as claimed in claim 1 wherein the angularly adjustable scale is adjustable over a small angle and is held by screws passing through slots in the member on which said scale is marked to permit said member to be locked in any position of adjustment within the range determined by said slots.

4. A machine as claimed in claim 1 wherein the end of the arm abuts against the end of the micrometer screw and is positioned between said end of said micrometer screw and the end of a second screw, the angularly adjustable scale being adjustable over a small angle and held by screws passing through slots in the member on which said scale is marked to permit said member to be locked in any position of adjustment within the range determined by said slots.

CLEMENT TIPTON RHODES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

